This invention relates to systems for, and methods of, irradiating products, primarily food products, to destroy harmful bacteria. More particularly, the invention relates to systems for, and methods of, irradiating objects, primarily food products, before the formation of the products into particular configurations and then forming the irradiated products into the particular configurations (such as hamburgers, chubs and case ready when the food products constitute meat).
It has been known for some time that drugs and medical instruments and implements have to be sterilized so that they will not cause patients to become ill from harmful bacteria when they are applied to the patients. Systems have accordingly been provided for sterilizing drugs and medical instruments and implements. The drugs and the medical instruments and implements have then been stored in sterilized packages until they have been ready to be used.
In recent years, it has been discovered that foods can carry harmful bacteria if they are not processed properly or, even if they are processed properly, that the foods can harbor and foster the proliferation of such harmful bacteria if they are not stored properly or retained under proper environmental conditions such as temperature. Some of the harmful bacteria can even be deadly.
For example, harmful bacteria have been discovered in recent years in hamburgers prepared by one of the large hamburger chains. Such harmful bacteria have caused a number of purchasers of hamburgers at stores in the chain to become sick. As a result of this incident and several other similar incidents, it is now recommended that hamburgers should be cooked to at least a medium state rather than a medium rare or rare state. Similarly, harmful bacteria have been found to exist in many chickens that are sold to the public. As a result of a number of incidents which have recently occurred, it is now recommended that all chickens should be cooked until no blood is visible in the cooked chickens.
To prevent incidents such as discussed in the previous paragraphs from occurring, various industries have now started to irradiate before the foods are sold to the public. This is true, for example, of hamburgers and chickens. It is also true of fruits, particularly fruits which are imported into the United States from foreign countries.
In previous years, gamma rays have generally been the preferred medium for irradiating. The gamma rays have been obtained from a suitable material such as cobalt and have been directed to the articles to be irradiated. The use of gamma rays has resulted in certain disadvantages. One disadvantage is that irradiation by gamma rays is slow. Another disadvantage is that irradiation by gamma rays is not precise. This results in part from the fact that the strength of the source (e.g. cobalt) of the gamma rays decreases over a period of time and that the gamma rays cannot be directed in a sharp beam to the article to be irradiated. This prevents all of the gamma rays from being useful in irradiating the articles.
In recent years, electron beams have been directed to articles to irradiate the articles. Electron beams have certain advantages over the use of gamma rays to irradiate objects. One advantage is that irradiation by electron beams is fast. For example, a hamburger patty can be irradiated instantaneously by a passage of an electron beam of a particular intensity through the hamburger patty. Another advantage is that irradiation by an electron beam is relatively precise because the strength of the electron beam remains substantially constant even when the electron beam continues to be generated over a long period of time.
When irradiation by an electron beam is provided, the articles being irradiated move on a conveyor line past a source of radiation. The articles move on the conveyor line at a relatively high speed and in a closely spaced relationship. When the articles constitute meat, the articles are preformed into different configurations such as hamburger patties, chubs and case ready articles. At any one time, only articles of a particular configuration are disposed on the conveyor line. It is inefficient to operate in this manner since the parameters of the conveyor line have to be changed when the articles on the conveyor lines are changed from one configuration to another configuration. Alternatively, a first conveyor line has been provided to irradiate food items such as hamburger patties; a second conveyor line has been provided to irradiate food such as chubs (articles having a long cylindrical configuration); and a third conveyor line has been provided to irradiate food items such as case ready meat products. Separate conveyor lines are inefficient, slow and costly.
There is another disadvantage to the systems now in use, particularly systems for irradiating meat. This results from the fact that the meat has been irradiated after it is introduced to the equipment which forms the meat into packets. For example, the meat has been ground in order to be formed into hamburger patties or chubs. After being ground and being formed into such specialized configurations as hamburger patties or chubs, the meat has then been transported to the conveyor line in which items of that particular configuration are being irradiated. This is inefficient, slow and costly, particularly because of the separate spaces and equipment needed to process and grind the meat, thereafter form the meat into particular configurations and then irradiate the ground meat of the different configurations.
A ground food product (e.g. meat) is leveled to a particular thickness and then irradiated. The leveler may be formed from two (2) spaced members (e.g., closed loop belts) spaced from each other by a distance progressively decreasing to a distance corresponding to the particular thickness. This distance may be adjustable to define any particular thickness for the food product. The leveler and the radiation source are disposed in a chamber providing shielding against radiation. The belt carrying the food product past the radiation source deposits the irradiated food product in a receptacle.
A transport mechanism (e.g. auger) transports the irradiated food product, without exposing the food product to harmful bacteria, from the receptacle to a to a former which provides the food product into individual configurations (e.g. hamburgers, chubs and case ready) without exposing the food product to harmful bacteria. The formed products are thereafter stored in an environment which excludes harmful bacteria. The belt carrying the food products may be reversed in direction when the radiation from the source is interrupted. The food products are then deposited in a second receptacle and are discarded.
In this way, the food product is irradiated only once and thereafter shaped into the desired configuration. The system is also advantageous, particularly in processing meat, since it continuously moves meat through the sequential steps of leveling and irradiating the ground meat and subsequently forming the meat into hamburger patties, chubs and case ready products. The steps after the radiation of the meat are accomplished in an environment where the meat is not exposed to harmful bacteria.